This article discusses recent advances in biocompatible and biodegradable polymer optical fiber (POF) for medical applications. First, the POF material and its optical properties are summarized. Then, several common optical fiber fabrication methods are thoroughly discussed. Following that, clinical applications of biocompatible and biodegradable POFs are discussed, including optogenetics, biosensing, drug delivery, and neural recording. Following that, biomedical applications expanded the specific functionalization of the material or fiber design. Different research or clinical applications necessitate the use of different equipment to achieve the desired results. Finally, the difficulty of implanting flexible fiber varies with its flexibility. We present our article in a clear and logical manner that will be useful to researchers seeking a broad perspective on the proposed topic. Overall, the content provides a comprehensive overview of biocompatible and biodegradable POFs, including previous breakthroughs, as well as recent advancements. Biodegradable optical fibers have numerous applications, opening up new avenues in biomedicine.

A simple plastic optical fiber (POF) based surface plasmon resonance (SPR) sensor is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. The sensor consists of a series of V-grooves along the POF and a side-polish structure at the other side of the fiber. The V-groove structure can alter the SPR excitation angle and act as a mode filter, effectively enhancing the SPR effect and narrowing the SPR wavelength width. After coating a layer of thermosensitive material—polydimethylsiloxane (PDMS) film on half part of the fiber probe, a dual-parameter sensor probe is obtained for RI and temperature measurement. Experimental results show the RI sensitivity of the prepared probe can reach 1546 nm/RIU in the RI range of 1.335–1.37 RIU and the temperature sensitivity is −0.83 nm/°C in the temperature range of 20–80°C. The sensor is simple in structure and low cost, and has potential applications in the biochemical sensing fields.

We report the first slightly tilted Bragg gratings photo-inscription in polymer optical fiber (POF). For this, we make use of trans-4-stilbenemethanol-doped photosensitive step-index poly(methyl methacrylate) (PMMA) POFs. Tilted fiber Bragg gratings (TFBGs) are inscribed in the near-infrared wavelength range using the scanning phase mask technique with a tilted phase mask in the plane perpendicular to the laser beam direction. The transmitted amplitude spectrum evolution of a 3° TFBG is analyzed as a function of the surrounding refractive index. A maximum sensitivity close to $13\mathrm{nm}/\mathrm{RIU}$ (refractive index unit) is obtained in the range 1.42–1.49.

We report the inscription of fiber Bragg gratings (FBGs) and Fabry-Perot (FP) cavities in a gradient index cyclized transparent optical polymer (CYTOP) polymer optical fiber (POF) using a femtosecond laser. Through careful control of the inscription parameters, the coupling between the grating and the fiber's higher order propagation modes is reduced, allowing for single peak grating spectra. Furthermore, we inscribe a 10-nm chirped grating and an FBG FP cavity with a free spectral range of 240 pm. We measure the group delay of the chirped grating and characterize the fiber FP cavity for strain and temperature.

Sleep quality plays an essential role in human health and has become an index for assessing physical health. Here, a pressure-sensitive, noninvasive, and comfortable smart pillow was developed based on an FBG sensor array to monitor head movements in real-time during sleep. The FBG array was embedded in the polydimethylsiloxane (PDMS)-based silicone button for improved pressure sensitivity and durability. The sensitivity of the pressure sensor was further optimized by modifying the structure of the button bulge and the thickness of the second layer. Both real-time monitoring of head position in a static state and head movement trajectory in a dynamic sleep state are realized. Finally, the fabricated sensor array was used for respiratory rate monitoring, with potential applications in personal healthcare diagnosis. This work not only provides a viable sensing device for sleep monitoring but could also be extended to real-time monitoring of some diseases, such as brain diseases and cervical spondylosis, in the future.